The school bus carrying inner-city children pulled up to a big blue building in Barrio Logan that housed a chrome-plating plant.

David Alvarez, 13, an eighth-grade student at Memorial Preparatory, sat a few rows back as a teacher explained how pollution from local businesses, such as that one, had caused higher-than-average rates of asthma among neighborhood children.

What he witnessed on the school trip and throughout his childhood would propel Alvarez on a journey to right social wrongs through public service and spur him to announce a surprise bid for San Diego mayor six weeks ago.

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The kids on the bus were all from low-income families participating in a UC San Diego program aimed at exposing them to science and technology and how they impact lives. As the teacher spoke, Alvarez, who unbeknown to the others lived next door to the plant, noticed a middle-aged woman walking down the street wearing an apron and a Burger King visor.

A young boy a couple of rows ahead of Alvarez piped up. “Why would anybody want to live here with this pollution?” The teacher replied that technological change can sometimes bring injustice and inequality.

As the bus pulled away, Alvarez got a closer look at the woman on the sidewalk and saw it was his mother walking home from work.

“At that moment I realized that there are a lot of inequalities in the city,” Alvarez said. “A lot of people are being left behind, and that’s still the case today. And in a San Diego that’s going to be great, we can’t allow that to happen. We cannot allow the same people who have controlled this city for far too long to continue to control the city.”

Now a city councilman, Alvarez, 33, is driven by this firsthand experience growing up in Barrio Logan. The Democrat’s politics have been shaped by a poor upbringing, having siblings involved in gang life and becoming the first in his family to go to college.

His agenda mirrors that of former Mayor Bob Filner, who resigned Aug. 30 amid a sexual harassment scandal, yet Alvarez comes without the personal baggage and character flaws. He’s banking on a “neighborhoods over downtown special interests” message resonating with voters again this year as it did for Filner. It’s a political mantra Alvarez has been using since his council race three years ago, well before it became a chic talking point.

The last high-profile candidate to announce, Alvarez began the mayor’s race as an underdog against well-heeled rivals but has since secured the backing of the Democratic Party and the San Diego and Imperial Counties Labor Council, the region’s largest labor organization, to make himself a major contender.

As Alvarez has shown time and again, the underdog role suits him well.

The political journey

Consider how far Alvarez has come since he first ran for City Council in 2010. He was actively opposed by the Labor Council, which spent nearly $113,000 to defeat him.

Now the Labor Council is willing to spend a half-million dollars or more on his mayoral bid.

His opponent in that council race, Felipe Hueso, was the politically-connected older brother of outgoing Councilman Ben Hueso. Alvarez ran a grass-roots campaign as a fresh-faced newcomer.

A devout Roman Catholic, Alvarez prayed a lot during the campaign. Not to win, but to stay grounded.

“No matter what, I wasn’t going to change who I was as an individual,” he said. “I was going to run as David Alvarez, the guy who people knew from the community. … I ran with that attitude and it was so peaceful. I was so at ease. All the time.”

Alvarez defied the odds, winning with 57 percent of the vote.

The newly elected councilman found a decidedly different challenge once he arrived at City Hall. He wanted to be a staunch advocate for the minority-rich southern San Diego neighborhoods he represented, but ran into Republican Mayor Jerry Sanders and a belt-tightening City Council that had other priorities. Alvarez ended up on the losing end of many votes and openly criticized Sanders, further isolating himself.

The major legislative victory for Alvarez during that time was the Property Value Protection Ordinance, which forces bankers to care for foreclosed properties or pay fees. He developed it with community input, which supporters say is a hallmark of his inclusive governing style.

Once Filner, a Democrat, took office last December, Alvarez took on a much larger role. As Filner’s closest council ally, he helped end the mayor’s protracted dispute with hoteliers over tourism marketing revenue, broker a five-year labor deal that gave city workers across-the-board raises for the first time in years and achieve a prevailing-wage ordinance for city contractors.

He was also one of the first council members to denounce Filner as the sexual harassment scandal erupted.

Critics point to the strong financial backing he’s received from organized labor and contend Alvarez will be beholden to the unions, which have resisted most efforts to reel in a pension system that has a long-term deficit in the billons.

Alvarez has matured quickly in less than three years on the council, but there remain doubters who question whether he has the know-how and experience to make good policy decisions. If elected, he would be the youngest San Diego mayor in 116 years.

“Clearly, some voters might have some concerns that David is only in his first term in elective office,” said Republican consultant John Dadian, who is not involved with any of the campaigns. “When you become mayor, especially with our relatively new strong mayor form of government, that’s a lot of power. You have to understand budgets and economics and a whole host of other issues, and that might be a concern on people’s minds.”

Those who have worked closely with Alvarez have no fear he’ll rise to any challenge. His old boss, former state Sen. Denise Moreno Ducheny, said Alvarez had the ability to grasp the big picture while also explaining the finer details on major budgetary and policy issues during his five years on her staff.

“David is very serious,” said Ducheny, echoing a description many others give about Alvarez. “The other big one, for me (is) actually caring about the constituents. Caring about getting people the answers and getting it done. Follow through.”

The personal journey

Alvarez’s parents came to the U.S. from Mexico and rented a small house on Newton Avenue between a mechanics shop and that chrome-plating plant. Every breath reminded him of his circumstances as pollution from the industrial businesses near his home he says gave him asthma.

Gang violence? He learned about that when his brother was shot in the leg during a drive-by. New clothes? Retail stores were out of the question, so his family shopped at garage sales in Clairemont and Point Loma, where he got glimpses of how other San Diegans lived.

At San Diego High School, Alvarez earned decent grades and excelled in math because he found the problem-solving satisfying. He also played in the marching band with a school-owned alto saxophone that had been used by generations of students.

He almost didn’t go to college. His parents, who never made it beyond third grade, viewed a high school degree as a pinnacle achievement; college was something other people did. Alvarez’s high school counselor disagreed and pushed him to apply to San Diego State. He got in.

National City Councilwoman Alejandra Sotelo-Solis, a family friend, said Alvarez later told her he felt a lot of pressure and responsibility from that moment forward. “He may be the youngest (of six siblings), but he takes the responsibility of a first child,” she said, adding that Alvarez’s widowed father now lives with him.

College showed him that you never know what doors open if you just try knocking. He presented his psychology research in Colorado. He used his math skills to rescue his middle school pal, a girl named Xochitl (pronounced SO-chee), from statistics. They started going out and eventually got married.

When he volunteered for a local political campaign, he caught the eye of Richard Barrera, now head of the Labor Council and board member of the San Diego Unified School District, who was then a community organizer.

“What struck me about David was both how bright he was, but also, really, his humility,” Barrera said. “This is not some hotshot kid going to college. He was very earnest, very much wanting to be engaged in work that was going to make the community better.”

Focusing on the man

Alvarez is selling himself more than anything else in his bid for mayor.

Until last week his campaign had yet to put out a detailed plan on any subject and spent most of its time telling his personal story and touting the support he’s received from prominent Democratic and labor groups. That may be because he doesn’t have the lengthy track record of his rivals.

What he does have is life experience similar to many who felt the brunt of the recent economic recession and ideals that promote helping the working poor, the homeless and the disenfranchised.

Xochitl Alvarez, an assistant principal expecting the couple’s second child, said her husband has been serving others since he was a teenager through community and church activities.

“He’s doing this because he really cares about San Diego, to see people really have a better opportunity,” she said. “It’s just how we are, how we grew up, helping other people.”

Specifically, Alvarez is advocating reinvesting in neighborhoods, addressing the city’s infrastructure backlog, increasing pay for police officers and asking residents about what they want done.

Not everyone thinks Alvarez has the community’s best interests at heart. The councilman recently struck a last-minute compromise on the Barrio Logan community plan to create a buffer between residences and shipyards. While many in the community support the plan, it continues to have opponents on both sides of the neighborhood-industry dispute.

“There’s a major trust factor with David,” said community activist Rachel Ortiz. “People who have worked not just these five years (on the plan) but as far back as 40 years, who renovated Barrio Logan, are insulted. It’s a slap in the face. That land was supposed to be ours, a testament to our progress over the decades. It was for his political gain, period. It’s obvious.”

Alvarez responded, “Leadership is not pandering to one specific group. My role as a leader is to make decisions based on the best interest of the majority.”

Spread the success

As youngsters, Alvarez and his brothers often rode their bicycles along Imperial Avenue and Harbor Drive, zipping by warehouses and industrial buildings and into the deserted roads of downtown’s East Village.

Through the years he saw those crumbling relics get rebuilt and modernized. Public investment created the Gaslamp Quarter to rejuvenate downtown, and one of the buildings he used to ride by — the Western Metal Supply Co. — became the left-field facade at Petco Park.

When it comes to revitalization, Alvarez calls downtown “the best job, if not the only success story.” But that success is a constant reminder of what he views as a broader failure: how other neighborhoods continue to struggle. Alvarez has made it his mission to shift the attention — and cash flow — to places and programs that have been overlooked for decades.

Those aren’t just empty words to Alvarez, as he witnessed up close the city’s unequal attention on communities. So here’s his pitch: Who better to focus on shifting City Hall’s focus toward neighborhoods than the boy on that bus who grew up — and still lives — on those streets?